Piston



June 3, 1930. wvcm scov 1,761,140

PISTON Filed Sept 7, 1926 4 Sheets-Sheet l June 3, 1930. ,W c. MCCOY 1,761,140

PISTON Filed Sept, 1926 4 SheetsSheet 2 June 3, 1930. w. c Mccv 1,761,140

PISTON Filed Sept 1926 4 SheetsSheet 3 June 1930 ISTO Filed Sept. 1926- 4 Sheets-Sheet 4 vide a piston of the flexible skirt type where-.

Patented 'June 3, 193 0 UNITEDQSTATES PATENT OFFICE WILLIAM G. MCCOY, OF CLEVELAND, OHIO, ASSIGNOR TO THE CLEVELAND TRUST GOI- PANY, OF CLEVELAND, OHIO, A CORPORATION OF OHIO PISTON Application filed September 7, 1926. Serial No. 138,909.

This invention relates to pistons for internal combustion engines and particularly to flexible skirt pistons that may, be formed from suitable aluminum alloys or any other desirable material.

One of the objects of the invention is to provide a piston that requires a minimum degree of care in fitting it to an engine cylinder and that is of inexpensive and simple construction. 1

Another object of the invention is to proin the skirt is compressible on its diameters in the general direction of the Wrist pin axis and transversely relative thereto.

An additional object of the invention is to provide a flexible'skirt piston in which the distortion of the skirt from cylinder wall pressure is more uniform than in previously.

proposed piston structures.

Another ob ect of the invention is to provide a piston in which the skirt is supported solely from connections to one of its bearing faces, the opposite bearing face being supported solely from connections to the first earing face and disconnected from other parts of the piston structure.

A further object of the invention is to provide a split skirt piston of balanced weight relative to the axis of the wrist pin.

An additional object of the invention is to rovide a piston of such character that it can e conveniently cast in a permanent mold.

These and other objects of the invention will be apparent from a consideration ofthe accompanying description taken in connection with the drawings, wherein Figure 1 is an eleva onal view, looking in the direction of the wrist'pin boss, of a piston constructed in accordance with the invention.

Fig. 2 is a bottom plan view of the pistonshown in Fig. 1 taken looking into the open end of the piston skirt.

Fig. 3 is a side elevational view of the piston 'shown in Fig. 1 taken looking in the direction of one of the working or hearing faces thereof.

Fig. 4 is a detail view of a portion of the piston skirt shown in enlarged transverse cross section taken substantially on line AA of Fig. 1.

Fig. 5 is a side elevational view of a corresponding piston structure illustrating a modified application of the invention.

Fig. 6 is a bottom plan view looking into the open end of the piston shown in Fig. 5.

Fig. 7 is a side elevational view of a piston structure corresponding to the structure shown in Fig. 5 except that no yielding bridge spans the longitudinal slit in the piston skirt. Fig. 8 is aside elevational view, lookingin the direction of a piston boss, of a modified formof the invention inwhich one side of the skirt. is connected both to the piston head and to webs formed integrally with the piston. bosses.

Fig. 9 is a side elevationalview, looking in the direction of the slit working face of the piston shown in Fig. 8.

Fig. 10 is a bottom plan view of the piston shown in Fig. 8 and F ig.-9 looking into the open end of the piston skirt. Fig. 11 is a side elevational view of a corresponding piston in which a yielding bridge spans the longitudinal slot in the piston skirt and in which both working faces of the piston are separated from the piston head.

. Fig. 12 is a side elevational view of the piston shown in Fig. 11.

Fig. 13 is a side elevational view of a further modification of the invention in which both working faces of the piston skirt are separated from the head by a transverse slot and in which the supported Working face of the piston is reinforced by a chordal rib and extends transversely thereacross.

Fig. 14 is a view looking into the open end of the piston shown in Fig. 13.

Fig. 15 is a side elevational view of a piswhich the longitudinal slit in the skirt is.

offset from both the working faceof the piston and the piston boss; and

' Fig. 16 shows the general form of piston illustrated in Fig. 15 with a yielding bridge spanning the longitudinal slit in the piston s irt.

The piston structure shown in Fig. 1 to Fig. 4, inclusive, of the drawings illustrates from the head whereas working face 22 is supported solely from working face 21 by the oppositely positioned segmental connectors 23 and 24 of the piston skirt. The working face 22 is yieldingly connected to the working face 21 by the radially flexible character of the web 24, and the yielding relation of the severed parts of the connector 23 that has a longitudinal slit 25 extending the entire l'en th thereof.

arch member 26 straddles the slit 25 on the inner side of the piston skirt to yieldingly connect the severed parts of the skirt element 23, as shown in Fig.4,and to provide a mutual support for the severed portions of the connecting element 23. Any tendency to longitudinal movement of the working face 22 relative to the working face 21 is efiectively resisted by the relatively wide connecting arch 26 whereas-the arch connector 26 will flex suficiently in response to cylinder pressure on the working face 22 of the skirt to prevent scoring or seizing of the piston.

The connecting arch also provides a mutual support for the severed portions of the skirt member 23 that facilitates finishing the piston to truly cylindrical or tapered cylindrical form. The casting strains that are generally present in a piston structure cause the severed skirt elements to move slightly out of alignment with each other when av slit is formed that separates the skirt longitudinally. The arch member supports each of the severed parts from the other severed part and thereby prevents objectionable local fiexing of the slit portions 23 of the skirt under the pressure of machine tools or of the grinding machine. 7

A longitudinal skirt stifiening or reinforcing rib 28 is formed on the inner side of the working face 21 of the skirt and extends to and joins with the head'20 of the piston to longitudinally reinforce the supported working face of the skirt and to forma more rigid longitudinal connection between the head and the Working face 21. The necessity for and the form and extent of the reinforcing rib working face 21 of the skirt from the piston Gil solely from the working face 21.

face 22 may be formed a sufficient degree thicker than the working face 21 to substantially balance the weight of the piston structure about the axis of the wrist pin. The skirt 22 is preferably made of increased thickness from the connector 23 to the center of the working face 22.

The particular feature of the piston structure that is emphasized herein is the support of one only of the working faces of the skirt and the complete operative separation of theother Working face of the skirt from both the head and the piston bosses beyond the longitudinal median plane of the piston passing through the wrist pin axis. The working face 22 of. the piston described is carried One working face is rigidly carried whereas the other face is yieldingly carried by the piston strucure.

The above described piston can be fitted with reasonable snugness to the cylinder in a cold engine. The mechanical tolerance of fit is thereby greatly reduced for quantity manufacture because the flexing of the piston skirt will take care of considerable variation in different relative cylinders and piston faces. The skirt will yield sufiiciently from the cylinder wall pressure to take a good polsh without scoring in a properly finished cylinder even when the piston is fitted to the cylinder tighter than is necessary for satisfactory operation.

- The substantially rigid connection of the working face 21 to the piston head makes it desirable, although not necessary, to mount the piston with the working face 21 so disposed as to take the side thrust of the explosive stroke whereas the less rigidl carried working face 22is connected to t e piston structure with sufficient rigidity to take the side thrust on the compressive stroke of the motor without substantial flexing. The presence of the single longitudinal slit 25 in the plston skirt and the twist resisting quality of the yieldlng arch 26 provides a very satisfactory connection for transmitting side thrusts from the working face 21 to the working face 22 of the skirt. The presence of the longitudinal slit 26 in the connecting portion 23 of the skirt renders the skirt uniformly flexible around its periphery and in the direction of both of its principal diameters.

Considerable pressure is ordinarily required to break down the oil film between the piston and the cylinder walls because of the large area of the working faceslof the piston.

23 depends upon the degree 0f rigidity 203$ When diametral forces from the direction of strength that is necessary to support the the wrist pin as well as at right angles thereto act to compress the piston, the piston structure can be made much stiffer than in pistons that are substantially compressible only along one major diameter. This stitier structure provides the more satisfactory strucios I Fig. 6 has the longitudinalslit 30 formed in the yieldingly supported working face 31. This form of pistonmay either be provided with an internal flexible arch 32 that permits closing in of the slot under compressive forces from the cylinder wall, or the piston may be formed withouti'a connection across the slit as shown in Fig. 7 The remainderof the structure of the pistons shown in Fig. 5,

Fig. 6 and Fig. 7 is substantially the same as the piston shown in Fig. 1 to Fig. 4, inclus1ve.

When the longitudinal slot is formed in the working face 31, the separated parts of the working face readily flex from radially applied pressure on every diameter of the piston, i. e. both in the longitudinal plane of the wrist pin and at right angles thereto.

Fig. 8, Fig. 9 and Fig. 10 illustrate a form I of piston'embodying the invention wherein the rigidly supported working face 33 of the piston is formed integrally with the head and a pair of oppositely disposed boss carrying webs 34. The opposed wrist pin bosses 35 are rigidly carried from the head. This provides a ver strong support forthis working face 33 0 the-piston. The working face 36 of the skirt is carried solely by the opposed skirt elements 37 that are integrally formed with the working face 33 and working face 36.

The side wall of the head of this piston structure may be somewhat thickened at 38 to substantially balance the piston about the axisof the wrist pin.

The piston structure shown in Fig. 11 and Fig. 12 diifers from the previously described piston by having a yielding arch member 39 spanning the longitudinal slit 40 of the skirt and also by having a slot 41 formed between the more rigidly supported working face 42 and the piston head. The working face 42 of the piston, skirt is supported solely from ,the webs 43 and the working face 44 is supported solely by connecting skirt portions 45. The entire skirt is maintained at a cooler operating temperature by arranging the slot between the top of the skirt and the head.

In this form of piston, the weight of the arch member 39 assists in. balancing the piston about the axis of the wrist pin. The

piston can also be counterbalanced on the side of the yielding working face by thick-- ening the side Wall of either the head or the working face of the skirt.

The piston structure shown in Fig. 13 and Fig. 14 is the same as the piston shown in Fig. 11 and Fig. 12 except that there is no yielding arch spanning the slit 46 of the working face 47 and that a chordal rib 48 is 5 formed across the working face 49. This minimizes flattening of the working face from thermal expansion of the piston head and causes the skirt supporting webs 50 to a take up the head expansion without transmitting it to the skirt. These webs are made sufliciently thin to flex sufiiciently to take up the head expansion without materially is offset from both the working face 54 and thewrist pin boss 55. The slit 52-is spaced from the slit -53 substantially the same or somewhat 7 less than the thickness of the skirt wall. This provides a' yielding element 56 that permits closing in of the skirt under cylinder pressure.

The piston shown in- Fig. 16 has the longitudinal slit 57 formed in the skirt underlying the wrist pin boss and spanned on the interior of the piston by a lyielding arch 58. The piston is otherwise similar to the piston shown in Fig. 13 and Fig. 14*. I.

It will be seen that in each of the foregoing piston structures, the piston skirt is so formedthat it is radially compressible both in the direction of the wrist pin bosses and transversely relative thereto. In conventional forms of split skirt pistons with which applicant is familiar, the piston skirt is only compressible along one principal diameter. By making one working face reterial to any desired part of the lighter side side relative to the wrist pin axis should be maintained substantially the same in various piston structures.

In each of the above forms of piston, little attention need be given the tolerances for the piston fittings. The structure is so formed that it will inherently accommodate itself if fitted too closely to the cylinder walls.

Other benefits that are to be derived from practicing the invention will be apparent of the piston.- The center of gravity of each from a consideration of the foregoingspecification and drawin of the various appllcations of the invention.

What I claim is:

1. A piston for an internal combustion engine comprising a head having depending wrist pin carrying bosses formed integrally therewith, a skirt portion integrally joined in a primary working face carried thereby, a said piston. skirt portion having a secondary worklng face carried solely by circumferentially exv tending segments of said primary skirt portion spaced from said head, and a longitudinal split separating the secondary skirt portion from the primary skirt portion.

2. A piston for an internal combustion engine Comprising a head, wrist pin bosses carried solely by said head, a skirt carried by said piston head solely from one working face thereof and joined to the head independently of said wrist pin bosses, and circumferentially extending segments spaced from said head and integrally united with said working face for solely supporting the other working face in free and unattached position relative to other parts of the piston structure, one of said segments being slotted to allow diametric yielding of said skirt without associated increase of its diameters at other points.

3. A single piece piston for an internal combustionengine comprising a head, wrist pin bosses relatively rigidly connected to said head, a skirt portion connected to said head at one side only and independently of said wrist pin bosses, said skirt portion being continuously separated from said head over ma terially more than 180 degrees of its circumference, circumferential segments spaced from said head and formed of the'metal of said side integrally connected with the other side of said skirt to support the same independently of other parts of said piston structure, one of said segments being split to permit yielding of said skirt, and an integral archimember straddling the split in said segment to yieldingly connect the severed portions of said segment. 7

4. A piston for an internal combustion engine comprising an integrally formed head and skirt, the skirt being provided with diametrically opposite working faces and being connected to the head through only one of said working faces, the other working face being carried from the first named working face of the skirt by circumferential continuations of the same in unattached positive relation to the other parts of the piston, and a longitudinal split separating the working faces.

5. A piston for an internal combustion engine comprising an integrally formed head and skirt, the skirt being provided with diametrically opposite working faces and being connected to the head through only one of said working faces, the other Working face being carried from the first named working face of the skirt by circumferential continuations of the same in unattached positive relation to the other parts of the piston, a longitudinal split separating the working faces, an integral member straddling the split In testimony whereof I aiiix my signature.

WILLIAM c. MOCOY.

to the head independently of said bosses havto yieldingly connect the severed portions of 1 

